Objective We developed the novel method for assessing myocardial synchrony (MD) using multi-slice CT (MSCT) and evaluated the validity of a MSCT indices based on dyssynchrony of regional fractional area change (RFAC) by comparing magnetic resonance myocardial tagging (MR-MT) based MD metric.
Background Despite the numerous documented benefits of cardiac resynchronization therapy (CRT), there remains a significant nonresponse rate to CRT with recent data questioning the reproducibility of standard echocardiography based MD metrics.
Although MSCT have a potential to provide a comprehensive information including the extent and location of scar tissue and cardiac vein anatomy, there is lacking of ability to assessing the presence of MD.
Methods MSCT and MR-MT were performed in a clinical cardiomyopathy cohort indicating ICD ± CRT (n=26; LVEF: 25 ± 7%). MR-MT and MSCT short axis images of left ventricle (LV) were reconstructed and defined myocardial contours semi-automatically. From MR-MT LV contours, circumferential uniformity ratio estimate (CURE) were determined as a reference of MD. Using customized MATLAB software, MSCT LV contours were analyzed using a fixed axis system with the centroid as the center point, using regional area method. The LV was divided into 24, 15°sector and regional fractional area change (RFAC) for each sector and their uniformity ratio estimate (RFACure) were calculated.
Results RFACure with a cutoff of less than 0.75 showed a 85% concordance rate with MR-MT CURE at this cutoff. In all subjects, MDCT-derived RFACure had a modest correlation with QRS duration (R=0.70, p < 0.001). Applying this RFACure cutoff to subjects underwent CRT based on clinical criteria (NYHA II-IV, QRS > 120ms, LVEF < 35%), RFACure predicted clinical improvement with 88% accuracy (PPV 80%; NPV 100%).
Conclusions The new MSCT based MD analysis method provide quantitative assessment of MD analogous to that obtained by MR-MT imaging. In addition to the scar imaging by delayed enhancement CT and cardiac vein imaging, this could provide a complementary information to improve targeting of CRT.
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